Scratch Detection by Eddy-Current Testing with a High Lift-Off Height

摘要

This paper describes an eddy-current testing (ECT) probe with a new structure, consisting of a perpendicular exciting coil and a spin-valve-type giant magneto-resistance sensor for scratch detection with a high lift-off height. We derived an analytical solution of eddy-current distribution to compare with a perpendicular exciting coil and a traditional parallel exciting coil. Experimental inspections with lift-off heights of 5 and 7 mm were carried out to detect scratches of 0.1 - 0.5 mm depth in a stainless steel plate. The 2-D experimental image results show that the proposed ECT probe has good detection capabilities.